ARM アーキテクチャで実行するために、Brisk 関数 (画像のサイズを変更する) を SSE 組み込み関数から ARM NEON 組み込み関数に変換しました。Brisk は、サポートされている場合は SSE 関数を使用し、サポートされていない場合は opencv 関数を使用します。もちろん、SSEの方が高速です。ARM ネオンの SSE 関数を段階的に変換しましたが、openCV のサイズ変更関数と比較して実行時間を測定すると、関数が遅くなります (0.2ms 対 0.4ms)。コードは次のとおりです。
SSE:
inline void BriskLayer::halfsample(const cv::Mat& srcimg, cv::Mat& dstimg){
const unsigned short leftoverCols = ((srcimg.cols%16)/2);// take care with border...
const bool noleftover = (srcimg.cols%16)==0; // note: leftoverCols can be zero butthis still false...
// make sure the destination image is of the right size:
assert(srcimg.cols/2==dstimg.cols);
assert(srcimg.rows/2==dstimg.rows);
// mask needed later:
register __m128i mask = _mm_set_epi32 (0x00FF00FF, 0x00FF00FF, 0x00FF00FF, 0x00FF00FF);
// to be added in order to make successive averaging correct:
register __m128i ones = _mm_set_epi32 (0x11111111, 0x11111111, 0x11111111, 0x11111111);
// data pointers:
__m128i* p1=(__m128i*)srcimg.data;
__m128i* p2=(__m128i*)(srcimg.data+srcimg.cols);
__m128i* p_dest=(__m128i*)dstimg.data;
unsigned char* p_dest_char;//=(unsigned char*)p_dest;
// size:
const unsigned int size = (srcimg.cols*srcimg.rows)/16;
const unsigned int hsize = srcimg.cols/16;
__m128i* p_end=p1+size;
unsigned int row=0;
const unsigned int end=hsize/2;
bool half_end;
if(hsize%2==0)
half_end=false;
else
half_end=true;
while(p2<p_end){
for(unsigned int i=0; i<end;i++){
// load the two blocks of memory:
__m128i upper;
__m128i lower;
if(noleftover){
upper=_mm_load_si128(p1);
lower=_mm_load_si128(p2);
}
else{
upper=_mm_loadu_si128(p1);
lower=_mm_loadu_si128(p2);
}
__m128i result1=_mm_adds_epu8 (upper, ones);
result1=_mm_avg_epu8 (upper, lower);
// increment the pointers:
p1++;
p2++;
// load the two blocks of memory:
upper=_mm_loadu_si128(p1);
lower=_mm_loadu_si128(p2);
__m128i result2=_mm_adds_epu8 (upper, ones);
result2=_mm_avg_epu8 (upper, lower);
// calculate the shifted versions:
__m128i result1_shifted = _mm_srli_si128 (result1, 1);
__m128i result2_shifted = _mm_srli_si128 (result2, 1);
// pack:
__m128i result=_mm_packus_epi16 (_mm_and_si128 (result1, mask),
_mm_and_si128 (result2, mask));
__m128i result_shifted = _mm_packus_epi16 (_mm_and_si128 (result1_shifted, mask),
_mm_and_si128 (result2_shifted, mask));
// average for the second time:
result=_mm_avg_epu8(result,result_shifted);
// store to memory
_mm_storeu_si128 (p_dest, result);
// increment the pointers:
p1++;
p2++;
p_dest++;
//p_dest_char=(unsigned char*)p_dest;
}
// if we are not at the end of the row, do the rest:
if(half_end){
// load the two blocks of memory:
__m128i upper;
__m128i lower;
if(noleftover){
upper=_mm_load_si128(p1);
lower=_mm_load_si128(p2);
}
else{
upper=_mm_loadu_si128(p1);
lower=_mm_loadu_si128(p2);
}
__m128i result1=_mm_adds_epu8 (upper, ones);
result1=_mm_avg_epu8 (upper, lower);
// increment the pointers:
p1++;
p2++;
// compute horizontal pairwise average and store
p_dest_char=(unsigned char*)p_dest;
const UCHAR_ALIAS* result=(UCHAR_ALIAS*)&result1;
for(unsigned int j=0; j<8; j++){
*(p_dest_char++)=(*(result+2*j)+*(result+2*j+1))/2;
}
//p_dest_char=(unsigned char*)p_dest;
}
else{
p_dest_char=(unsigned char*)p_dest;
}
if(noleftover){
row++;
p_dest=(__m128i*)(dstimg.data+row*dstimg.cols);
p1=(__m128i*)(srcimg.data+2*row*srcimg.cols);
//p2=(__m128i*)(srcimg.data+(2*row+1)*srcimg.cols);
//p1+=hsize;
p2=p1+hsize;
}
else{
const unsigned char* p1_src_char=(unsigned char*)(p1);
const unsigned char* p2_src_char=(unsigned char*)(p2);
for(unsigned int k=0; k<leftoverCols; k++){
unsigned short tmp = p1_src_char[k]+p1_src_char[k+1]+
p2_src_char[k]+p2_src_char[k+1];
*(p_dest_char++)=(unsigned char)(tmp/4);
}
// done with the two rows:
row++;
p_dest=(__m128i*)(dstimg.data+row*dstimg.cols);
p1=(__m128i*)(srcimg.data+2*row*srcimg.cols);
p2=(__m128i*)(srcimg.data+(2*row+1)*srcimg.cols);
}
}
}
アームネオン:
void halfsample(const cv::Mat& srcimg, cv::Mat& dstimg){
const unsigned short leftoverCols = ((srcimg.cols%16)/2);// take care with border...
const bool noleftover = (srcimg.cols%16)==0; // note: leftoverCols can be zero but this still false...
// make sure the destination image is of the right size:
//assert(srcimg.cols/2==dstimg.cols);
//assert(srcimg.rows/2==dstimg.rows);
//int32x4_t zero = vdupq_n_s8(0);
// mask needed later:
//register __m128i mask = _mm_set_epi32 (0x00FF00FF, 0x00FF00FF, 0x00FF00FF, 0x00FF00FF);
int32x4_t mask = vdupq_n_s32(0x00FF00FF);
// to be added in order to make successive averaging correct:
int32x4_t ones = vdupq_n_s32(0x11111111);
print128_numhex(mask);
// data pointers:
int32_t* p1=(int32_t*)srcimg.data;
int32_t* p2=(int32_t*)(srcimg.data+srcimg.cols);
int32_t* p_dest=(int32_t*)dstimg.data;
unsigned char* p_dest_char;//=(unsigned char*)p_dest;
int k=0;
// size:
const unsigned int size = (srcimg.cols*srcimg.rows)/16;
const unsigned int hsize = srcimg.cols/16;
int32_t* p_end=p1+size*4;
unsigned int row=0;
const unsigned int end=hsize/2;
bool half_end;
if(hsize%2==0)
half_end=false;
else
half_end=true;
while(p2<p_end){
k++;
for(unsigned int i=0; i<end;i++){
// load the two blocks of memory:
int32x4_t upper;
int32x4_t lower;
if(noleftover){
upper=vld1q_s32(p1);
lower=vld1q_s32(p2);
}
else{
upper=vld1q_s32(p1);
lower=vld1q_s32(p2);
}
int32x4_t result1=vaddq_s32(upper, ones);
result1=vrhaddq_u8(upper, lower);
// increment the pointers:
p1=p1+4;
p2=p2+4;
// load the two blocks of memory:
upper=vld1q_s32(p1);
lower=vld1q_s32(p2);
int32x4_t result2=vaddq_s32(upper, ones);
result2=vrhaddq_u8(upper, lower);
// calculate the shifted versions:
int32x4_t result1_shifted = vextq_u8(result1,vmovq_n_u8(0),1);
int32x4_t result2_shifted = vextq_u8(result2,vmovq_n_u8(0),1);
// pack:
int32x4_t result= vcombine_u8(vqmovn_u16(vandq_u32(result1, mask)),
vqmovn_u16(vandq_u32 (result2, mask)));
int32x4_t result_shifted = vcombine_u8(vqmovn_u16(vandq_u32 (result1_shifted, mask)),
vqmovn_u16(vandq_u32(result2_shifted, mask)));
// average for the second time:
result=vrhaddq_u8(result,result_shifted);
// store to memory
vst1q_s32(p_dest, result);
// increment the pointers:
p1=p1+4;
p2=p2+4;
p_dest=p_dest+4;
//p_dest_char=(unsigned char*)p_dest;
}
// if we are not at the end of the row, do the rest:
if(half_end){
std::cout<<"entra in half_end" << std::endl;
// load the two blocks of memory:
int32x4_t upper;
int32x4_t lower;
if(noleftover){
upper=vld1q_s32(p1);
lower=vld1q_s32(p2);
}
else{
upper=vld1q_s32(p1);
lower=vld1q_s32(p2);
}
int32x4_t result1=vqaddq_s32(upper, ones);
result1=vrhaddq_u8(upper, lower);
// increment the pointers:
p1=p1+4;
p2=p2+4;
// compute horizontal pairwise average and store
p_dest_char=(unsigned char*)p_dest;
const UCHAR_ALIAS* result=(UCHAR_ALIAS*)&result1;
for(unsigned int j=0; j<8; j++){
*(p_dest_char++)=(*(result+2*j)+*(result+2*j+1))/2;
}
//p_dest_char=(unsigned char*)p_dest;
}
else{
p_dest_char=(unsigned char*)p_dest;
}
if(noleftover){
row++;
p_dest=(int32_t*)(dstimg.data+row*dstimg.cols);
p1=(int32_t*)(srcimg.data+2*row*srcimg.cols);
//p2=(__m128i*)(srcimg.data+(2*row+1)*srcimg.cols);
//p1+=hsize;
p2=p1+hsize*4;
}
else{
const unsigned char* p1_src_char=(unsigned char*)(p1);
const unsigned char* p2_src_char=(unsigned char*)(p2);
for(unsigned int k=0; k<leftoverCols; k++){
unsigned short tmp = p1_src_char[k]+p1_src_char[k+1]+
p2_src_char[k]+p2_src_char[k+1];
*(p_dest_char++)=(unsigned char)(tmp/4);
}
// done with the two rows:
row++;
p_dest=(int32_t*)(dstimg.data+row*dstimg.cols);
p1=(int32_t*)(srcimg.data+2*row*srcimg.cols);
p2=(int32_t*)(srcimg.data+(2*row+1)*srcimg.cols);
}
}
}
ARM 関数と SSE 関数の出力はまったく同じです。問題は実行時間です。